The invention relates to a press brake tool holder and a tool commonly referred to as xe2x80x9cAmerican-stylexe2x80x9d tooling.
Press brakes commonly are equipped with a lower table and an upper table, one of which, commonly the upper table, is vertically movable toward the other table. Forming tools are mounted to the tables so that when the tables are brought together, a workpiece between the forming tables is bent into an appropriate shape. It is common for the upper table to include a male forming tool having a bottom workpiece-deforming surface, usually V shaped, and for the bottom table to have an appropriately shaped die having an upper surface vertically aligned with the workpiece deforming surface of the tool so that when the tool and die are brought together, a workpiece between the two is pressed by the forming tool into the die and thus is given an appropriate bent shape.
It often is necessary to exchange forming tools and dies when a different bending operation is to be performed. The dies, commonly supported by the bottom table of a press brake, are readily removed and exchanged for others. However, the forming tools that usually are mounted to the upper table of a press brake often are not easily replaced. Forming tools usually are held by a C clamp or other holder to the horizontally elongated upper table. Once the clamp has been loosened, the forming tool can, in some instances, be removed downwardly, and in others, must be removed by horizontally sliding it from the clamp. If a long forming tool is to be replaced, it becomes difficult to slide the forming tool from its clamp because of the proximity of neighboring clamps and forming tools; these, in turn, may themselves have to be removed in order to complete the tool exchange process.
Because long forming tools can be quite heavy, when a clamp is loosened to the point that the tool can be removed by moving it downwardly, a tool may accidentally slip and fall, causing harm to press brake operators and equipment.
An early press brake holder design is known as the xe2x80x9cAmerican stylexe2x80x9d and is shown schematically in FIG. 1A holding a common American-style press brake tool. As shown in this figure, the bottom edge portion of the upper table is so fashioned as to accept a clamp C, and a heavy bolt is employed to attach the clamp to the table. The press brake table and clamp respectively include generally parallel, facing surfaces defining a downwardly open recess into which the tang T of a press brake tool is received. The bottom surfaces B of the press brake table and clamp commonly are horizontally aligned, and serve as load bearing surfaces for transmitting a downwardly directed load onto the upwardly facing shoulders S of a press brake tool. To mount the tool in the holder, the tool is pushed upwardly until its load receiving surfaces S encounters the load transmitting surfaces B of the clamp and table, as depicted, and the bolt then is tightened to clamp the punch tool tang between the clamp and table.
From a manufacturing standpoint, the simplified design of the American-style press brake tooling requires that the upwardly facing shoulders be fairly accurately horizontally aligned, but the tolerances on the height of the tang of the tool are relatively wide. As a result, long sections of American-style tooling can be manufactured, and when a press brake operator needs a particular length of tooling, the appropriate length simply is cut from the long section and used directly. When the tool is to be removed from the holder, the clamp C is loosened and the tool, firmly gripped by the press brake operator, is withdrawn downwardly. To avoid the possibility of accidental dropping of the tools, which can be quite heavy in long lengths, a strap can be attached to the top of the tang with the edge of the strap extending into a groove in the holder. However, with this arrangement, the tool can be removed only by sliding it sideways from the holder or by disassembling the entire holder.
American-style tool holders thus are of a simple design having few moving parts, and are relatively easy to use. Of the various types of press brake tooling and tool holders available, the American style is the most widely used and remains a favorite.
FIG. 1B is a schematic side view of a press brake tool and tool holder commonly referred to as a xe2x80x9cEuropeanxe2x80x9d or xe2x80x9cPromecamxe2x80x9d style. The press brake tool itself has an upwardly extending tang T that is generally rectangular in cross section and that has a safety groove extending along its length. Below the safety groove, the tool has an outwardly extending, upwardly facing shoulder S, and the tool extends downwardly from that shoulder to its workpiece-encountering edge. European style tool holders commonly include a lip or edge that extends into the safety groove of the tool to restrain accidental dropping of the tool. As with American-style tooling, the downwardly directed force of the ram is directed against an upwardly facing shoulder or shoulders of the tool, rather than against the upper surface of the tang. Examples of European style tooling are shown in U.S. Pat. Nos. 6,003,360 (Runk et al.) and 5,794,486 (Sugimoto et al.).
A third style of tooling, commonly referred to as Wila style tooling, is shown in FIG. 1C. Reference also is made to U.S. Pat. No. 5,245,854 for a description of this type of tooling and tool holder. The tool holder includes one or more horizontally extending safety slots, and the tool itself includes a movable projection that, in use, extends outwardly from a side wall of the tool into the safety slot. The upper end of the tang T of this tool style extends into force-receiving contact with the tool holder; that is, the downward force of the upper table is transmitted directly to the upper surface of the tang.
European-style and Wila-style tool holders enable tools to be removed downwardly from the holders. Although these tool holders have provided some safety features to restrain a heavy tool from accidentally falling from the tool holder, no such system has been devised for the more popular American-style tooling and tool holders. It will be understood that when small tools are being employed, the risk of injury from dropping the tool is not great, whereas when longer and heavier lengths of tooling are used, the risk of injury resulting from a tool that unintentionally drops from the tool holder is substantially greater.
It would be valuable to provide tooling that would be adaptable for use in American-style press brake tool holders, but that yet would offer the ability to loosen the clamp on the American-style tool holder without risking immediate dropping of the tool.
We have noted that, in American-style press brake tool holders, there exists, in the downwardly open recess receiving the tool tangs, a shelf having an upwardly facing surface, and we have devised a tool having a safety key that can engage the upper surface of the shelf to restrain the tool from unintentional dropping when the clamp is loosened, while not interfering with the transfer of a downwardly directed force from the upper table to the tool.
The present invention provides, in combination, a press brake tool and an American-style press brake tool holder from which the tool can be removed vertically rather than requiring the tool to be slid horizontally from the holder. The holder has a body with walls defining a downwardly open, tool-receiving recess having a top, a downwardly facing, force-delivering shoulder adjacent the bottom of the recess, and a shelf within the recess having an upwardly facing surface that is spaced upwardly from the force-delivering shoulder. The tool comprises a body having a lower, work-engaging surface, an upwardly facing, force-receiving shoulder that is engageable with the shoulder of the tool holder, and an upwardly extending tang that is receivable in the recess and that has an upper end that is spaced from the top of the recess. The tool includes a manually operable actuator that is spaced below the force-receiving shoulder of the tool so that it may be accessed and manually operated by a worker, and also a safety key that is operatively coupled to the actuator. The safety key has a lower surface that is spaced above the upper end of the tang and that is engageable with the upwardly facing surface of the shelf. The key is movable horizontally into and out of vertical alignment with the shelf between locked and unlocked positions, respectively, in response to manual operation of the actuator. Thus, the current invention makes use of the shelf that is normally part of the American-style tool holder, and does so in a manner that provides a long-awaited safety solution to tool-dropping problems associated with this most popular press brake tool and tool holder combination involving release and removal of a tool downwardly from the tool holder rather than requiring removal by sliding the tool sideways in the tool holder.